Overmature Trees Research Articles

Changes in Chinese fir plantations root exudation strategies seasonally and as tree age

Root exudates play an important role in nutrient acquisition and defense of trees. However, there are few studies on the mechanism of productivity decline in late stage from the perspective of root exudates. Therefore, we collect root exudates in the summer and winter from 8-year-old (young), 18-year-old (middle-aged), and 49-year-old (overmature) trees in Chinese fir plantations to assess how their exudation rates and metabolite composition changed across these different life stages. Results showed that the rates and metabolite composition of root exudation varied significantly across plantation ages and between seasons. Specifically, the young Chinese fir trees increased exudation rates and produced more carbohydrates and quercetins, and overmature trees secreted more lipids and salicylic acids. This indicates that young Chinese fir plantations adopted root metabolic strategies which increased nutrient acquisition to satisfy the demands of rapid growth, but overmature plantations might produce more defensive metabolites to improve their defense capabilities. Additionally, in the winter, trees had slower root exudation rates and released a smaller proportion of organic acid, carbohydrate, and quercetin metabolites than in the summer, but a greater proportion of lipid and salicylic acid metabolites. We also found that soil microbial factors (microbial community composition and diversity) had a significant effect on the composition of primary and secondary metabolites in the winter. Overall, as plantation age increased, Chinese fir root metabolic strategies related to nutrient acquisition decrease, while those related to defense increase. These findings provide a new perspective for our understanding of the mechanisms that lead to productivity declines of Chinese fir plantations in later growth stages.

Fire Severity Controls Successional Pathways in a Fire-Affected Spruce Forest in Eastern Fennoscandia

Tree stand dynamics, changes in the ground vegetation and soils, and species diversity of wood-decaying fungi were studied in pristine middle boreal spruce forests affected by a surface fire in the Vodlozersky National Park (Arkhangelsk Region, Russia) in 2011. In the third year after the fire, the burnt area was dominated by birch, which contributed an average of 72% to the total amount of major tree species regeneration. In sites affected by a high-severity fire, the ground vegetation cover did not exceed 40%, with Chamaenerion angustifolium (L.) Scop. and Marchantia polymorpha L. dominating in the first years after. By the tenth year, the diversity of the newly forming tree layer increased from 5 to 11 species and natural thinning of deciduous tree regeneration was already underway, although its amount was still over 100,000 plants per hectare throughout. By the end of the first post-fire decade, Picea abies (L.) H. Karst. and Pinus sylvestris L. accounted for 11% of the total regeneration. The occurrence and cover of pyrogenic species Chamaenerion angustifolium and Marchantia polymorpha declined sharply at this stage. Vegetation in sites affected by mid-severity fire was mostly regenerating through propagation of the survivor Avenella flexuosa (L.) Drejer, Vaccinium myrtillus L., V. vitis-idaea, etc. In the burnt area, the species diversity of wood-destroying fungi was reduced compared to the adjacent unburned areas, and it was the same in both heavily and moderately burnt areas. This is probably due to the fact that the downed deadwood in post-fire sites was trunks of the same age and in the same degree of decay whereas the total amount of downed deadwood in the control (unburnt forest) was lower but featuring all stages of decay and, furthermore, there were plenty of fungi-populated dead standing and weakened overmature trees.

Water sources of Populus euphratica with different tree ages in the oasis of desert hinterland.

Understanding vegetation water utilization can provide scientific basis for vegetation protection and rational distribution of water resources in arid desert oasis area. In this study, sapling (DBH≤10 cm), mature (10 cm<DBH≤40 cm), and overmature (DBH>40 cm) Populus euphratica were chosen as sample trees in natural oasis of Dariaboui. We measured oxygen isotopes of xylem water and potential water sources (surface water, soil water in 0-3 m soil layer and groundwater) of P. euphratica with different tree ages. The IsoSource model was used to study water sources of P. euphratica. The results showed that soil water content increased with increasing soil depth, while the δ18O value of soil water decreased firstly and then stabilized. When groundwater depth was 2 m, the δ18O value of xylem water increased with increasing tree ages. When the depths of groundwater were 4.2 and 8 m, the δ18O values of xylem water decreased with increasing tree ages. Water sources of P. euphratica varied across tree age. When the depth of underground water was 2 m, the main water source for young trees was surface water, and the contribution proportion was 64.7%. For mature and overmature trees, it was deep soil water and ground-water, with a contribution of about 30%. When the depth of groundwater was 4.2 m, the main water sources of P. euphratica of different tree ages were deep soil water and groundwater, and the contribution proportion was about 30%. The lowest contribution of P. euphratica of different tree ages was shallow soil water, accounting for about 10%.

AGE-SPECIFIC DYNAMICS OF ESSENTIAL OIL CONTENT IN ABIES SIBIRICA BARK. THEORETICAL ASPECTS OF EVALUATION

The variability of the essential oil content in Abies Sibirica bark in the Eastern and Western parts of the Krasnoyarsk forest-steppe was evaluated in eight age groups. The model of the age dynamics of changes in the essential oil content in the bark of Abies Sibirica, which is adequate to the experimental data, was obtained. With increasing age of fir, the content of fir oil in the bark increases from 1.4±0.1% of a. s. s. in 20–30 years of age to 2.8±0.2% of a.s.s. at the age of 70–80 years, with further decreases to 0.4±0.1% of a. s. s. in overmature trees.&#x0D; The results of parametric identification of the model for Abies Sibirica growing in the Krasnoyarsk forest-steppe are presented. Based on the results of 50.000 computational experiments, the simulation method estimates the statistics of changes in the model coefficients and 95% of the boundary of the forecast values of the content of fir oil in the bark. A compartment model is proposed that explains the age-specific dynamics of essential oil content in tree greens and Siberian fir bark. The obtained solution compartment model allows us to associate its parameters with the coefficients of models of changes in the content of fir oil in tree greens and bark obtained by processing experimental data.

Spatial distribution of carbon dynamics and nutrient enrichment capacity in different layers and tree tissues of Castanopsis eyeri natural forest ecosystem.

Forest ecosystem carbon (C) storage primarily includes vegetation layers C storage, litter C storage, and soil C storage. The precise assessment of forest ecosystem C storage is a major concern that has drawn widespread attention in global climate change worldwide. This study explored the C storage of different layers of the forest ecosystem and the nutrient enrichment capacity of the vegetation layer to the soil in the Castanopsis eyeri natural forest ecosystem (CEF) present in the northeastern Hunan province, central China. The direct field measurements were used for the estimations. Results illustrate that trunk biomass distribution was 48.42% and 62.32% in younger and over-mature trees, respectively. The combined biomass of the understory shrub, herb, and litter layers was 10.46 t·hm-2, accounting for only 2.72% of the total forest biomass. On average, C content increased with the tree age increment. The C content of tree, shrub, and herb layers was 45.68%, 43.08%, and 35.76%, respectively. Litter C content was higher in the undecomposed litter (44.07 %). Soil C content continually decreased as the soil depth increased, and almost half of soil C was stored in the upper soil layer. Total C stored in CEF was 329.70 t·hm-2 and it follows the order: tree layer > soil layer > litter layer > shrub layer > herb layer, with C storage distribution of 51.07%, 47.80%, 0.78%, 0.25%, and 0.10%, respectively. Macronutrient enrichment capacity from vegetation layers to soil was highest in the herb layer and lowest in the tree layer, whereas no consistent patterns were observed for trace elements. This study will help understand the production mechanism and ecological process of the C. eyeri natural forest ecosystem and provide the basics for future research on climate mitigation, nutrient cycling, and energy exchange in developing and utilizing sub-tropical vegetation.

Effects of ontogenetic stage and leaf age on leaf functional traits and the relationships between traits in Pinus koraiensis

Investigating the effects of ontogenetic stage and leaf age on leaf traits is important for understanding the utilization and distribution of resources in the process of plant growth. However, few studies have been conducted to show how traits and trait-trait relationships change across a range of ontogenetic stage and leaf age for evergreen coniferous species. We divided 67 Pinus koraiensis Sieb. et Zucc. of various sizes (0.3–100 cm diameter at breast height, DBH) into four ontogenetic stages, i.e., young trees, middle-aged trees, mature trees and over-mature trees, and measured the leaf mass per area (LMA), leaf dry matter content (LDMC), and mass-based leaf nitrogen content (N) and phosphorus content (P) of each leaf age group for each sampled tree. One-way analysis of variance (ANOVA) was used to describe the variation in leaf traits by ontogenetic stage and leaf age. The standardized major axis method was used to explore the effects of ontogenetic stage and leaf age on trait-trait relationships. We found that LMA and LDMC increased significantly and N and P decreased significantly with increases in the ontogenetic stage and leaf age. Most trait-trait relationships were consistent with the leaf economic spectrum (LES) at a global scale. Among them, leaf N content and LDMC showed a significant negative correlation, leaf N and P contents showed a significant positive correlation, and the absolute value of the slopes of the trait-trait relationships showed a gradually increasing trend with an increasing ontogenetic stage. LMA and LDMC showed a significant positive correlation, and the slopes of the trait-trait relationships showed a gradually decreasing trend with leaf age. Additionally, there were no significant relationships between leaf N content and LMA in most groups, which is contrary to the expectation of the LES. Overall, in the early ontogenetic stages and leaf ages, the leaf traits tend to be related to a "low investment-quick returns" resource strategy. In contrast, in the late ontogenetic stages and leaf ages, they tend to be related to a "high investment-slow returns" resource strategy. Our results reflect the optimal allocation of resources in Pinus koraiensis according to its functional needs during tree and leaf ontogeny.

Обеспеченность подростом предварительной генерации спелых и перестойных светлохвойных насаждений Осинского лесничества Пермского края

On the basis of forest inventory data of the main Osinsky forestry, an attempt was made to analyze light coniferous stands and the availability of mature and overmature trees of a preliminary generation among them. The basis of the research is the analysis of a high-performance database using SQL queries to determine statistically reliable information using spreadsheets and geographic information systems. It has been established that the share of light coniferous plantations in the forestry area of the coniferous-deciduous (mixed) forest area in the European part of the Russian Federation does not exceed 14 % of the total area covered by forest vegetation and they are mainly represented by middle-aged pine forests of growth class I with a full stand of 0,7. About 72 % of light coniferous stands grow in the type of forest conditions B2. The proportion of larch in the total area of light coniferous stands, not exceeding 0,5 %, was determined. They are predominantly represented by medium-density young growths and middle-aged stands of I and II growth class and are confined to the type of forest conditions C2. A rather high availability of undergrowth with preliminary generation was shown only 8,11 % of ripe and mature light coniferous plantations do not have undergrowth. Spruce dominates in the composition of the undergrowth of preliminary generation, which occurs in 88,72 % of the area of ripe and overmature pine trees, and its density exceeds 3700 % / ha by 37,6 %. A significant proportion of plantations with the presence of undergrowth of spruce in the types of forest conditions with poor dry, moist and wet sandy soils require the replacement of pine with its undergrowth in order to avoid changing light coniferous plantations to less productive dark coniferous ones. Pine growth occurs in 3,2 % of the area of ripe and mature light coniferous plantations, which necessitates measures to facilitate its accumulation. In particular, it is possible to recommend mineralization of the soil under the seed year for pine, which will further minimize the cost of artificial reforestation. Data on the availability of undergrowth by groups of forest types and relative completeness make it possible to optimize the regime of selective fellings.

Spontaneous landscape dynamics in the Pays de Bitche, Lorraine (France), during the Little Ice Age

ABSTRACT This study is an analysis of a historical document (the ‘Atlas topographique du comté de Bitche’), dating from 1758 and carried out in north-eastern France. The Atlas is composed of three large volumes. The aim was to evaluate the timber resources that had accumulated during the 100 years of land abandonment following the Thirty Years’ War (1618–1648). Before the seventeenth century, the main woodland management was a form of the selective cutting of over-mature trees. The authors of the Atlas focused on oak (without differentiating Quercus petraea from Q. robur) and beech (Fagus sylvatica) sexual regeneration, dead wood and the characteristics of woodlands. According to size, the woodlands (so-called ‘futaies’) were divided into five categories to which the authors associated arbitrary age ranges. Other information concerned climatic events (storms, frosts and drought), large illegal cuttings and new rules for land use. These descriptions were converted into semi-quantitative data by counting the number of mentions of the woodland categories. The main result was that futaies with large-sized trees, specifically oaks, were dominant. Tree-ring counting on twenty-four selected beech and oak trees indicate that there was no relationship between age and size. Another interesting result was that during the 100 years of non-use, oaks died massively probably following competition with beech, harsh climatic events typical of the Little Ice Age or insect attacks.

The Estimation of the Initial Stage of Succession of Green-pine Trees Windfall in the Eastern Moscow Suburbs

The paper is devoted to the study of entomocomplex of stem pests, the number and biology of its dominant species and the ecological structure of the soil mesofauna of the two differing in composition and growing conditions, areas of wind pine forests-green insects. The main causes of windfalls, which are unfavorable soil and soil conditions and the defeat of trees by the root sponge, are established. The degree of participation of different types of feed substrate in the dynamics of the number of stem pests in the lesion is estimated. In addition to the windfall of trees, stem pests are the adjacent one, decreasing the resistance of pine in the walls of the forest, overmature trees or trees weakened by anthropogenic, standing trees, the trunks of which are damaged by windfall to a lesser extent than the remaining standing part of inboard of broken trunks. We identified eight species of entomophagous parasitic on the grubs of Longhorn beetles and jewel beetles. It is noted that the population of ground beetles, in windswept areas studied, is characterized by a decrease in species diversity, a decrease in the number of moisture-loving species typical of pine forests of the Eastern Moscow region, a change in the spectrum of life forms in the direction of reducing litter species and increasing the proportion of litter-soil.

The analysis of factors influencing the sustainability of forest stands

The problem of the ecological state of the microclimate of the modern metropolis and surrounding areas is becoming more and more urgent every year due to the increasing anthropogenic impact. This is why it is necessary to conduct a systematic assessment of the state of green spaces in order to design a set of measures to improve their sustainability, preserve biological diversity and improve the environment. The study of tree planting was carried out in an instrumental and visual way. The assessment of natural renewal was carried out on a differentiated scale of the state and quality of natural renewal under the canopy of forest plantations. The purpose of the study was to identify factors that affect the intensity of damage to tree stands, predict the volume of dead trees, and develop an approach to improving the stability of forest stands. As a result, is has been stated that storm damage has mainly affected weak, mature and overmature trees. Root rot (i.e., spruce root rot) promotes high degree of windthrow, while stem rot provokes windbreak (which is typical for hardwood species – aspen, birch, lime tree). The greatest influence on the intensity of damage to plantings by windfall and windbreak has the length of the crown, the diameter of the trunk and the content of rot. Based on the results of the research a new approach of regenerating species composition and the structure of local forest types at the national park has been proposed.

Site and age-dependent responses of Picea abies growth to climate variability

Knowledge about spatiotemporal variability of climate change effect on tree-ring width (TRW) and crown condition is essential to optimize the modelling of future forest ecosystem responses to the changing climate. Geographical differences in the climate–growth relationship are a reflection of the regional climatic conditions mainly. In this study, 175 Picea abies trees from the north-western edge of its geographical distribution in Central Norway were evaluated with respect to geographical and age-dependent differences during the common period of 1950–2015. The results showed that the most significant positive correlations between TRW and the current June temperature were unstable although the temperature increased. The correlations suddenly started to decrease (regardless of the site placement and tree age) at the beginning of the 1990s, but subsequently unexpectedly increased in the 2010s. The superposed epoch analysis revealed longer TRW regeneration of the southern plots (except over-mature trees) after negative pointer years compared to the northern plots. Previous summer temperature and related physiological processes (cone crops, storage of nutrients, etc.) significantly negatively affected P. abies growth in the current year. Additionally, our results showed that the selection of the chronology version (standard or residual) significantly affects the resulting correlations and thus must be carefully considered in dendroclimatological studies. Our main outputs can contribute to better understanding of the climate–growth relationship variability and general prediction of the radial growth.

Effects of forest management on bryophyte species richness in Central European forests

We studied the effect of three major forest management types (unmanaged beech, selection beech, and age class forests) and stand variables (SMId, soil pH, proportion of conifers, litter cover, deadwood cover, rock cover and cumulative cover of woody trees and shrubs) on bryophyte species richness in 1050 forest plots in three regions in Germany. In addition, we analysed the species richness of four ecological guilds of bryophytes according to their colonized substrates (deadwood, rock, soil, bark) and the number of woodland indicator bryophyte species. Beech selection forests turned out to be the most species rich management type, whereas unmanaged beech forests revealed even lower species numbers than age-class forests. Increasing conifer proportion increased bryophyte species richness but not the number of woodland indicator bryophyte species. The richness of the four ecological guilds mainly responded to the abundance of their respective substrate. We conclude that the permanent availability of suitable substrates is most important for bryophyte species richness in forests, which is not stringently linked to management type. Therefore, managed age-class forests and selection forests may even exceed unmanaged forests in bryophyte species richness due to higher substrate supply and therefore represent important habitats for bryophytes. Typical woodland indicator bryophytes and their species richness were negatively affected by SMId (management intensity) and therefore better indicate forest integrity than the species richness of all bryophytes. Nature conservation efforts should focus on the reduction of management intensity. Moreover, maintaining and increasing a variability of substrates and habitats, such as coarse woody debris, increasing structural heterogeneity by retaining patches with groups of old, mature to over-mature trees in managed forests, maintaining forest climate conditions by silvicultural methods that assure stand continuity, e.g. by selection cutting rather than clear cutting and shelterwood logging might promote bryophyte diversity and in particular the one of woodland indicator bryophytes.

The larger, the better? Effects of delayed diameter-limit cutting on old-growth attributes and saproxylic beetle diversity in temperate oak forests

Intensive management implies harvesting large, old trees, which reduces the old-growth attributes. This negatively affects biodiversity, especially saproxylic beetles. In managed temperate oak forests, rotation extension induced by increasing the diameter threshold of final harvest by about 10 cm compared to conventional practices (i.e. DBH around 70 cm) might mitigate this negative effect. Here, we used a gradient of the proportion of overmature trees (DBH ≥ 80 cm) among mature trees (DBH ≥ 70 cm) across plots of high oak French forests to test the potential effect of increasing diameter threshold on (1) structural features and (2) species composition and diversity of saproxylic beetles communities. We assessed deadwood and microhabitats availability (i.e. volume/density and diversity) and canopy openness in 81 1-ha plots across eleven French forests. Results highlighted that a larger proportion of overmature trees, for a given density of mature trees, had limited effects on structural features: only cavities density showed a significant positive response, with no cascading effect on cavicolous beetles. Moreover, the proportion of overmature trees had no significant effect on the composition of saproxylic beetles communities (and ecological variables altogether explained only 17% of the composition inertia). By contrast, mature tree density enhanced microhabitat density and indirectly increased the abundance of rare species. Thus, shifting DBH from 70 to 80 cm in high oak forest could have no or limited effect on saproxylic beetles conservation. Improved strategies might rather stem from combining (1) longer rotation extension and (2) less intensive management practices in extended rotation stands.

The Carbon Sinks and Mitigation Potential of Deodar (&amp;lt;i&amp;gt;Cedrus deodara&amp;lt;/i&amp;gt;) Forest Ecosystem at Different Altitude in Kumrat Valley, Pakistan

Forest carbon monitoring and reporting are critical for informing global climate change assessment. The regional estimates of forest carbon attached greater attention, to assess the role of forest in carbon mitigation. Here using field inventory, we examined the carbon sink and mitigation potential of monospecific Deodar forest in the Kumrat valley, of Hindu Kush Himalaya, Region of Pakistan, at a different elevation. The elevation of monospecific Deodar forest ranges from 2300 to 2700 m (a.s.l). We divided the forest into three elevation classes (that is 2300 - 2400 m (EI) 2400 - 2500 m (EII) and 2500 - 2700 m (EIII) a.s.l respectively). In each elevation class, we laid out 09 sample plots (33*33 m2) for measuring carbon values in living tree biomass (LT), soil (SC), litter, dead wood, cone (LDWC) and understory vegetation (USV). Our results showed that the carbon density at EI was 432.37 ± 277.96 Mg·C-1, while the carbon density at EII and EIII was 668.35 ± 323.94 and 1016.79 ± 542.99 Mg·C-1 respectively. Our finding revealed that the carbon mitigation potential of the forest increases with increasing elevation. Among the different elevation classes, EIII stored significantly higher carbon due to the dominance of mature, old age, larger trees, and the minimum anthropogenic disturbance, whereas EI stored statistically lower carbon because of maximum anthropogenic disturbance, which resulted in the removal of mature and over-mature trees. Furthermore, our correlation analysis between tree height and carbon stock and basal area and LT carbon, underlines that the basal area is the stronger predictor of LT carbon estimation than height. Overall our results highlight that deodar forest stored 716.94 ± 462.06 Mg?C·ha-1. However, the rehabilitation, preservation and sustainable management of disturb forest located at a lower elevation could considerably improve carbon mitigation potential.

Effects of precipitation changes on the dynamics of sparse elm woodland in Northeastern China

Elm (Ulmus pumila L.) is the dominant tree species in the sparse elm woodland, the original vegetation in the Horqin Sandy Land. The effects of changes in precipitation on U. pumila trees have not been fully studied. We determined a dynamic model by considering the five stages in the U. pumila life cycle, i.e. seed, seedling, and juvenile, mature and over-mature tree stages. The effects of changes in precipitation on population density and age structure were then evaluated. Population density, after averaging all study developmental morphology stages, ranged from 16.67 individuals/m2 to 25.01 individuals/m2 under a mean annual precipitation (MAP) of 80% to 120%, respectively. This suggests that population density could increase as MAP also increased. The proportion of seedlings, and juvenile, mature and over-mature trees were 95.23%, 4.58%, 0.19% and 0.01%, respectively, under all precipitation levels. This indicates that precipitation had little effects on the developmental stages of the studied U. pumila populations in the Horqin Sandy Land. Additional water supply might be provided in addition to the natural rainfall that occurs in the region, for contributing to maintain U. pumila population density in the Horqin Sandy Land.

“Primeval forest relict beetles” of Central Europe: a set of 168 umbrella species for the protection of primeval forest remnants

Identification of forest stands with priority for the conservation of biodiversity is of particular importance in landscapes with a long cultural and agricultural history, such as Central Europe. A group of species with a high indicator value for the naturalness of forest ecosystems are saproxylic insects. Some of these species, especially within the order Coleoptera, have been described as primeval forests relicts. Here, we compiled a list of 168 “primeval forest relict species” of saproxylic beetles based on expert knowledge. These species can serve as focal and umbrella species for forest conservation in Central Europe. They were selected because of their dependence on the continuous presence of primeval forest habitat features, such as over-mature trees, high amounts of dead wood, and dead wood diversity, as well as their absence in managed Central European forests. These primeval forest relict species showed a moderately strong clumping pattern within the phylogeny of beetles, as indicated by phylogenetic signal testing using the D-statistic. When we controlled for phylogenetic relatedness, an ordinal linear model revealed that large body size and preference for dead wood and trees of large diameter are the main characteristics of these species. This list of species can be used to identify forest stands of conservation value throughout Central Europe, to prioritize conservation and to raise public awareness for conservation issues related to primeval forests.

Effects of Thinning and Water Supply Manipulation on the Productivity of Pinus sylvestris var. mongolica in Northeastern China.

Management is an effective tool for increasing the productivity of Mongolian pine (Pinus sylvestris var. mongolica). This species has been widely planted in China, especially in sandy lands. However, optimization of management practices had not been fully explored. We established a system dynamic model to evaluate the effects of thinning and of manipulation of water supply on the productivity and population density of a Mongolian pine forest (17 scenarios in total). Different levels of thinning increased the mean biomass of Mongolian pine over no-management to a range from 202 to 256 t·ha-1. Increasing water supply decreased the mean biomass of Mongolian pine to a range from 176 to 199 t·ha-1. These results indicated that thinning at different levels may lead to an increase in biomass accumulation, while manipulating water supply may decrease biomass. Further, thinning appeared more effective than increasing water supply in efforts at maintaining high productivity of Mongolian pine forests. Moreover, the highest biomass occurred in a scenario with a thinning intensity of 30% in over-mature trees, indicating that this thinning intensity was the most effective choice for to the maintenance of the highest biomass in Mongolian pine forests. This study informs about the interactions between Mongolian pine and forest management, and provides guidelines for the practice of management of this forest type.

Multi-scale reference conditions in an interior pine-dominated landscape in northeastern California

A plot-based census was conducted of trees >8.9cm in breast height diameter in a 4000ha forest in northeastern California in 1933 and 1934, prior to any harvest activity. The trees were tallied by size class and species on contiguous plots specified to be 1.01ha in size, although some plots had a forested area less than this specification due to natural openings in the forest. In general, variability in all metrics declined as scale increased across a range from 1ha to 244ha, although much of this variability was in the tails; the inner quartile range appeared to be more stable, particularly so for crown area. Although metrics were derived at a smaller scale (<1ha) from partial plots, these may be unreliable due to the study design and possible confounding factors. The landscape distribution of tree sizes was bimodal and skew positive with a maximum tree size of 189.2cm. However locally the distribution of tree sizes was more ragged and variable in shape. Species distribution appears to have shifted in a direction away from pine dominance in the years since the census was conducted. Historically, these stands were approximately 86 percent pine by basal area, with some variation depending on slope position. The stem density was dominated by young, thrifty-mature trees of good or moderate vigor but basal area and crown area was dominated by mature or over-mature trees with moderate or poor vigor. Crown area tended to be low with 90 percent of observations between 13 and 35 percent at the 1ha scale.

Logging by selective extraction of best trees: Does it change patterns of genetic diversity? The case of Nothofagus pumilio

Extensive knowledge of the ecological and genetic consequences of implementing management practices (i.e. logging) in natural ecosystems is of fundamental importance to conservation action. Accordingly, characterization of forest genetic resources in managed vs non-managed stands may inform management decisions to ensure the long-term persistence of genetic diversity. The main objective of this study was to evaluate the impact of management practices on the genetic diversity and spatial genetic structure of contrasting forests, through an age-class sampling design and the use of microsatellite markers. We evaluated the impact of logging in three populations of Nothofagus pumilio, a dominant tree species in Patagonian temperate forests, by comparing managed and non-managed stands in each population. Selective extraction of best-featured individuals, i.e. those with forestry aptitude, such as higher trees with straight trunks and good sanitary conditions, was performed between 1990 and 2004. One of the studied sites was located in a state-protected area while the others were on private land affected by grazing. At each managed stand over-mature trees (MF-O), adult remnant trees (MF-A) and seedlings representing forest regeneration (MF-R) after silvicultural management were sampled. In non-managed stands age classes were restricted to adults (CF-A) and seedlings (CF-R). A minimum of 30 individuals per age class were collected, totalling 454 samples which were genotyped at six microsatellite loci.Non-significant differences in genetic diversity were found between managed and natural woods in all populations. A trend towards decreasing frequencies or even allele loss among remnant adults of logged stands can however be interpreted as a sign of impact, probably a consequence of genetic drift. Each site showed particular, different outcomes with respect to genetic structure. While in Pop 1 (Huemules, 42°S) significant genetic differentiation was found between management treatments, admixture of genetic clusters (Bayesian clustering and DAPC analysis) occurred in Pop 2 (Guacho Lake, 43°S) and no genetic structure was found in Pop 3 (Engaño Lake, 43°S). Post-harvest genetic contact between contrasting stands is likely. A Landscape Interpolation Analysis showed clusters of individuals (shared genotypes) spatially restricted for managed stands (significant in Pop 3), whereas a random spatial distribution characterized control forests. Therefore, it is possible that management affected and disrupted the genetic structure.The different genetic patterns revealed for each population call for site-by-site interpretation. Differential intensity and frequency of management practices, presence/absence of livestock in the forest, and evolutionary history may all have had combined effect on current genetic diversity.

How to Regenerate and Protect Desert Riparian Populus euphratica Forest in Arid Areas.

We found that the most suitable flooding disturbance model for regenerating Populus euphratica forest was two to three times per year with a duration of 15–20 days and an intensity of 25–30 m3/s. The flooding should take place during the seed emergence to young tree growth stages, and should be based on flooding experiments and data from vegetation quadrats and ecological water conveyance. Furthermore, we found that tree-ring width index for P. euphratica declined as the groundwater depth increased, and ascertained that the minimum groundwater depths for young trees, near-mature trees, mature trees and over-mature trees were 4.0 m, 5.0–5.4 m, 6.9 m and 7.8 m, respectively. These were derived from a quantitative relationship model between groundwater depth and tree-ring width index. The range for ecological water conveyance volume was 311–320 million m3 in the lower reaches of the Tarim River. This study not only provides a technical basis for sustainable ecological water conveyance in the Tarim River Basin, but also offers a theoretical guide and scientific information that could be used in similar areas to regenerate and protect Populus euphratica around the world.